Researchers around the world will be scrutinising the health effects of the Chernobyl disaster - the world's worst nuclear accident - to develop a more accurate picture of the long-term hazards from radiation exposure and the impact this might have on international safety limits at nuclear power stations.
Scientists found children living in the region of the former Soviet republic of Belarus, which borders the Ukraine, are 80 times more likely to develop the disease than children elsewhere in the world.
Thyroid cancer normally occurs in about one child in a million per year, but the scientists report in the journal Nature that this has risen to 80 per million since 1990.
Since 1986, when the Chernobyl disaster sent a radioactive cloud over much of Europe, the Belarus Ministry of Health has monitored levels of thyroid cancer. Because of its link with radioactive iodine, it is usually the first cancer to appear after radiation exposure.
Scientists say there will not be a similar increase in thyroid cancers in Britain. The fall-out cloud took a week to arrive and much of its radioactive iodine had either dispersed or decayed.
Between 1986 and 1989, the Belarus scientists, led by Vassili Kazakov, reported an average of four cases per year. In 1991, this rose to 55 and they expect at least 60 cases by the end of this year.
Dr Kazakov and his colleagues say in the article: 'The occurrence of this increase in thyroid cancer in children within a few years of exposure to radioactive isotopes of iodine is unexpected, but real. It poses both humanitarian and scientific problems, and is placing great strains upon the health services of our new country.'
The researchers add: 'We believe that the only realistic explanation for the increase in the frequency of thyroid cancer is that it is a direct consequence of the accident at Chernobyl.'
Scientists working for the World Health Organisation have independently confirmed the figures. Dillwyn Williams, professor of pathology at the University of Wales College of Medicine, said the increase was 'very much more than we would have expected from previous studies'.
Keith Baverstock, a radiation scientist sent to validate the results, said he would normally expect to see thyroid cancers about 10 years after exposure to radiation, rather than four.
'It is unexpected that it is so early. It may indicate the start of a much bigger thing, or it may be that there is a particularly sensitive sub-group within the population we were unaware of,' he said.
If it is the former, it has 'tremendous implications for the country of Belarus in terms of the amount of resources needed to deal with the condition'. If it is the latter, 'it has implications for the rest of the world', he said.
Dr Baverstock said the childhood cancers in question were 'very aggressive' and had often affected the tissue surrounding the thyroid, a gland in the neck responsible for hormone production. One child in the study has died and another 10 out of a total of 131 are seriously ill, the Belarussian researchers report. The highest cancer rate is in the Gomel region, which borders Ukraine and is about 100 kilometres from Chernobyl.
Dr Baverstock said the thyroid cancers could have resulted from the release of short-lived isotopes of iodine from Chernobyl that would have been inhaled before decaying after a day or two.
An alternative possibility is that the children consumed food, most probably milk, contaminated with the longer-lived iodine isotope (iodine-131) which takes weeks to decay, he said.Reuse content